Faults with electric windows and central locking are quite common and are usually caused by broken/shorting wiring in the door pillar to door gaiter, constant opening/closing of the doors eventually weakens the wiring till it either breaks or the insulation cracks and splits.

The location/access makes it quite difficult and how far you need to dismantle.
Disconnect battery first
Now start by turning the locking ring anticlockwise carefully with hammer and screwdriver once loosened you should be able to turn by hand, you will need to pull the door in at this stage as the plug will foul the edge of the door, once removed let the door go right back open.
If not already done gently pull the gaiter from the door and slide it to the plug.
It should be pretty obvious which wires are damaged but now you have to decide if you have the room/ability/skill to repair at this stage, removing the gaiter completely requires removing the locking ring from the plug and pulling the gaiter over the plug without splitting the gaiter and without putting strain on the already weak wiring this is not easy even with using silicone spray which does help considerably, the down side is it the makes it difficult to grip the gaiter with your fingers.
Another option is to remove the door card and unplug the wiring and pull through this will give you more slack and is the better option if needing to repair lots of wires

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If you decide to remove the gaiter you will need to remove the locking ring by pressing the three tabs simultaneously just enough to slide off the locking ring, spray the inside of the gaiter with silicone spray then ease the gaiter over the plug, there is no real gain in completly removing the gaiter as you will find it extremely difficult to get back on the plug.

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Gaiter removed for clarity
I cut out the broken section leaving enough wire at each end to splice in new cable, don't forget to slide on the heat shrink tubing before soldering.

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Repairs completed pull the gaiter back over the plug ensuring the gaiter fits over the first lip then refit the locking ring to the plug

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Check the pillar socket ring is still tight before entering the plug back in

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Pull the door inward slightly while refitting the plug do not force it in as you risk bending the pins

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Once the locking ring has engaged turn clockwise tighten fully, finish by easing the gaiter into the door until it's in the  groove!